The capuchin monkey, indigenous to Central and South America, is a rather distant relation of humankind. We are Old World primates--more closely related to chimpanzees, orangutans, and even baboons.
Nevertheless, we have much to learn from capuchins.
They are the largest-brained, smartest monkeys in the New World.
And they have independently evolved many traits--like tool use--that were once regarded as uniquely human.
Why? There are many reasons, but one of them should interest all parents. Like people in many human cultures, capuchins are remarkably tolerant of juvenile curiosity.
UCLA anthropologist Susan Perry has been watching wild capuchins for almost 20 years—ever since she founded the Lomas Barbudal Capuchin Monkey Project in Costa Rica. She's observed monkeys from infancy to adulthood, tracking what juveniles learn as they grow up. Along the way, she and her colleagues have documented some remarkable similarities between capuchins and humans (Perry and Manson 2008).
These large-brained, social monkeys
• Use tools to get food. Like humans, capuchin monkeys are omnivores, and many of the foods they eat require mechanical processing—like pounding, prying, or scrubbing. To be an effective forager, a young capuchin monkey must learn how to tackle each food type. In some cases, capuchins actually use tools—like a hammer stone to open a nut or seed.
• Share. Experiments show that capuchins will spontaneously share treats with familiar group members (deWaal et al 2008). Capuchins share food in the wild, too, and show more spontaneous prosocial behavior than do chimpanzees (Burkart and van Schaik 2012; Sabbatini et al 2012).
• Use “daycare.” After a capuchin monkey infant is born, group members compete for a “turn” with the baby, inspecting and handling it whenever the mother permits. As babies become more independent, they initiate these interactions. Non-maternal “babysitters” may carry babies up to 9% of the time. And babies are regularly nursed by females other than their own mothers (Perry and Manson 2008).
• Form friendships, alliances, and social cliques. Capuchins don’t just make friends. They also know something about the friendships between other monkeys. For example, consider this scenario: You are about to get into a fight. You look around to see if there are any people nearby who could help you. Whom should you ask for help? You might pick your closest available buddy. But what if that person is also friends with your opponent? Wild capuchins seem to think about these complications. In an analysis of 110 real-life capuchin monkey battles, researchers confirmed that monkeys don’t just pick their best friends. Rather, they solicit aid from individuals with whom they are better friends than their opponents are (Perry et al 2004).
• Learn to use “words.” As she grows up, a young capuchin monkey needs to learn several different “words,” or alarm calls that warn group members about the presence of predators. One call seems to mean “Look out, it’s a dangerous bird!” Other calls are about dangerous humans, cats, or snakes. It’s pretty clear that monkeys have to learn these meanings because kids make mistakes. About 20% of juvenile alarm calls are made in response to inappropriate targets. As kids get older, their alarm-calling becomes more accurate (Perry and Manson 2008).
Parents will recognize some other behaviors, too—like nipple tweaking. While nursing, an infant capuchin monkey doesn’t just drink milk. He also “preps” the other nipple, by kneading it with his hand. This stimulates milk production, and it seems to have a calming effect.
But one of the most surprising discoveries concerns social traditions.
Perry and her colleagues have discovered that some wild capuchin groups engage in strange social rituals, like “hand sniffing,” in which a monkey slips its finger over—or inside—another monkey’s nose.
It’s not just a random act. When hand sniffing, the normally boisterous monkeys are very quiet and still, sometimes for as long as ten minutes. Monkeys are more likely to engage in hand sniffing with their favorite grooming partners, and partners typically play both roles—by taking turns or putting their fingers in each other’s nostrils simultaneously.
Perry suspects that these rituals function as many human rituals do--opportunities to demonstrate commitment to each other (Perry and Manson 2008).
How kids learn: Do capuchins have culture?
It seems that capuchin babies have a lot to learn--about tool use, politics, predators, and social relationships. Do they have to learn it all by themselves, or do they get a little help from their friends?
Humans take culture for granted. Kids don’t have to reinvent the wheel every generation. They learn from us. Have capuchins evolved the capacity for culture? Perry thinks they do.
For example, capuchins can open the edible seeds of the Luehea fruit in one of two ways—by pounding or scrubbing. Both ways are equally effective, but young monkeys eventually settle on just one technique—whichever technique they’ve most frequently observed other monkeys using (Perry 2009).
These findings are supported by experiments on captive capuchins. In one study, researchers presented a capuchin monkey with a box that could be opened in two ways—by lifting or sliding a door. The monkey was trained to get food from the box using just one method. Then he was paired with a naïve monkey—somebody who had never seen the box before.
Despite being free to open the box anyway he liked, the observer monkey showed a strong preference for the demonstrator’s method. When the observer was subsequently paired with another “new” monkey, this newcomer also preferred to use the method he’d seen modeled. In this way, the capuchins spread a “tradition” along a chain of up to 5 observers (Dindo et al 2007).
So it appears that capuchins really do transmit something akin to culture—learned behaviors that are passed from monkey to monkey. It even seems that capuchins “learn from the best.” A study of nut-cracking--in which wild capuchins use stone tools to open nuts--found that juveniles were more likely to watch the most proficient nut crackers (Ottoni 2005).
So why are capuchins like humans?
Why is the capuchin monkey so similar to humans? Some similarities reflect our common ancestry. For instance, it seems likely that mammal babies have been kneading their mothers’ nipples for millions of years.
But the last common ancestor of humans and capuchins lived over 30 million years ago. It was small-brained and rather lemur-like.
Many similarities—like large brains, tool use, and high social intelligence—were probably not present in the last common ancestor of capuchins and humans.
Instead, these traits evolved independently, after our lines diverged—like two separate experiments with similar outcomes.
The phenomenon is called convergent evolution, and it makes capuchins especially useful. That’s because cases of convergent evolution permit us to test hypotheses about the conditions necessary for traits to evolve. What’s the common denominator linking each case?
For example, what can explain the evolution of tool use? If you take a look at the primate family tree, it appears that the capacity for tool use has evolved at least three times—once in apes (a group that includes humans and chimpanzees), once in baboons and their close relatives (the cercopithecine monkeys) and once in capuchins (van Schaik et al 1999).
What do tool-using primates have in common? Yes, they are all dexterous. And they tend to eat foods that need to be extracted or pried open.
But the most frequent tool users have something else in common--something that’s a little less obvious: They are socially tolerant.
Social tolerance: The key to tool use and social learning?
Picture this: A monkey invents a new tool or a new way to get food. Does anybody else learn the new trick?
For animals to learn from each other, they have to get close enough to see what’s going on. And they can’t do that if everybody is uptight, nervous, or unfriendly.
So researchers like Carel van Schaik have argued that social tolerance is a prerequisite for socially-transmitted tool use.
Tool use is more common in primate societies that are “laid back,” societies where dominant individuals are more tolerant of subordinates, where individuals reconcile after conflicts, and where adults allow juveniles to get close and observe what they are doing (van Schaik et al 1999).
Capuchins fit this model well. Although capable of violence, capuchins are also very tolerant of nosy youngsters. And the kids are very nosy indeed. It’s not unusual for juveniles to sit alongside an adult who is processing food, their eyes glued to the action. The kids will watch with great intensity while the adult works—plenty of opportunity to observe technique.
Does it apply to humans? It certainly seems to. A recent analysis of over 80 years of research on classroom learning reveals that kids tend to learn better in cooperative, noncompetitive settings (Roseth et al 2008). So perhaps social tolerance was what gave our ancestors—and the ancestors of apes, baboons, and capuchins—the edge.
Much more to learn—if we can keep the research going...
And public support has already made a big difference.
Currently, Susan Perry’s team is in the middle of a long-term study of infant development--a study that examines how social factors influence what capuchins learn about food, predators, and politics.
The study is very promising, because Perry’s team already knows so much about the individuals and the groups they live in. The Lomas Barbudal project has collected over 60,000 hours of behavioral information, as well as genetic profiles and hormonal data.
But what about the future? Will research get derailed by destruction of monkey habitats? Poaching?
When I first wrote this article in 2009, the Lomas Barbudal monkeys were under threat. Forest was being destroyed, and poachers were killing monkeys.
Now there is good news. Strong advocacy and letter-writing campaigns have stopped the destruction.
On July 23, 2010, the Costa Rican park service and several private organizations will sign an agreement promising future protection for the capuchins. Perry and her team have gotten permission to re-forest the area damaged by mining, and they've received large donations of trees from government and private tree nurseries to begin the process.
Interested in the project?
The monkeys' future is looking much brighter than it did in 2009. But it's not too late to contribute. The Lomas Barbudal Monkey Fund aids research, educational outreach, and local conservation. You can make a donation through Perry’s capuchin monkey webpage at UCLA.
More to readIf capuchins have captured your imagination, you check out Perry's book, Manipulative Monkeys: The Capuchins of Lomas Barbudal
Written with co-researcher Joe Manson, this book combines theoretical discussions with detailed accounts of the monkeys' daily lives.
The book is especially valuable for its frank depiction of the challenges and frustrations of fieldwork. Want to know how field workers collect their data? Eat? Sleep? Raise families while watching wild animals? Perry and Manson answer these questions with vivid detail and wry humor.
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deWaal, F, Leimgruber K and Greenberg AR. 2008. Giving is self-rewarding for monkeys. PNAS 105(36): 13685-13689.
Dindo M, Theirry B and Whiten A. 2007. Social diffusion of novel foraging methods in brown capuchin monkeys (Cebus paella). Proc. R. Soc. B. 275: 187-193.
Ottoni EB, de Resende BD, Izar P. 2005. Watching the best nutcrackers: What capuchin monkeys (Cebus apella) know about others' tool-using abilities. Anim Cogn 24:215-219.
Perry S, Barrett HC, and Manson JH. 2004. White-faced capuchin monkeys exhibit triadic awareness in their choice of allies. Animal Behaviour 67:165-170.
Perry S. 2009. Conformism in the food processing techniques of white-faced capuchin monkeys (Cebus capucinus). Animal Cognition. May 20 2009 (Epup ahead of print].
Perry S, with Manson J. 2008. Manipulative monkeys: The capuchins of Lomas Barbudal. Harvard University Press.
Roseth CJ and Johnson DW, and Johnson RT. 2008. Promoting Early Adolescents' Achievement and Peer Relationships: the Effects of Cooperative, Competitive, and Individualistic Goal Structures. Psychological Bulletin 134(2):223-246.
Sabbatini G, De Bortoli Vizioli A, Visalberghi E, and Schino G. 2012. Food transfers in capuchin monkeys: an experiment on partner choice. Biol Lett. 8(5):757-9. doi: 10.1098/rsbl.2012.0534.
Van Schaik CP, Deaner RO, and Merrill MY. 1999. The conditions for tool use in primates: implications for the evolution of material culture. Journal of Human Evolution 36: 719-741.
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